Controller pattern for route handlers in Express - Mini Project: Build & Apply

Controller pattern for route handlers

📖 Scenario: You are building a simple Express web server that manages a list of books. To keep your code clean and organized, you want to separate the route handling logic into a controller.

🎯 Goal: Create an Express server with a controller pattern where route handlers are defined in a separate controller object. You will set up the data, configure a controller, connect routes to controller methods, and complete the server setup.

📋 What You'll Learn

Create an array called books with three book objects, each having id and title properties

Create a controller object called bookController with a method getAllBooks that sends the books array as JSON

Set up an Express route GET /books that uses bookController.getAllBooks as the handler

Complete the Express server setup to listen on port 3000

💡 Why This Matters

🌍 Real World

Separating route logic into controllers helps keep Express apps organized and easier to maintain, especially as they grow.

💼 Career

Understanding the controller pattern is essential for backend developers working with Express or similar web frameworks.

1

DATA SETUP: Create the books array

Create an array called books with these exact objects: { id: 1, title: 'The Hobbit' }, { id: 2, title: '1984' }, and { id: 3, title: 'Pride and Prejudice' }.

Express

// Your code here

Need a hint?

Use const books = [ ... ] with three objects inside the array.

2

CONFIGURATION: Create the bookController object

Create a constant object called bookController with a method getAllBooks that takes req and res parameters and sends the books array as JSON using res.json(books).

Express

const books = [
  { id: 1, title: 'The Hobbit' },
  { id: 2, title: '1984' },
  { id: 3, title: 'Pride and Prejudice' }
];

// Your code here

Need a hint?

Define bookController as an object with a method getAllBooks that calls res.json(books).

3

CORE LOGIC: Set up the Express route using the controller

Import Express, create an app with express(), and add a route GET /books that uses bookController.getAllBooks as the handler.

Express

const books = [
  { id: 1, title: 'The Hobbit' },
  { id: 2, title: '1984' },
  { id: 3, title: 'Pride and Prejudice' }
];

const bookController = {
  getAllBooks(req, res) {
    res.json(books);
  }
};

// Your code here

Need a hint?

Use const app = express() and app.get('/books', bookController.getAllBooks).

4

COMPLETION: Start the Express server

Add app.listen(3000) to start the server on port 3000.

Express

const express = require('express');
const books = [
  { id: 1, title: 'The Hobbit' },
  { id: 2, title: '1984' },
  { id: 3, title: 'Pride and Prejudice' }
];

const bookController = {
  getAllBooks(req, res) {
    res.json(books);
  }
};

const app = express();
app.get('/books', bookController.getAllBooks);

// Your code here

Need a hint?

Use app.listen(3000) to start the server.